Lost Communication with Special Purpose Module C
The U025B code indicates that the special purpose 'C' control module has lost communication with the vehicle's CAN data bus. This auxiliary controller manages specific functions not covered by main modules, such as specialized body systems, commercial vehicle conversions, or adaptive equipment. The loss of communication means data messages between this module and other controllers (ECM, BCM, etc.) are no longer transmitting correctly, which can affect functions dependent on this module.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty special purpose 'C' control module (internal damage, hardware failure)
- CAN bus wiring interruption (open circuit, short to ground or battery)
- Damaged CAN bus terminator or termination resistor
- Corroded or loose connector pins in the module harness
- Low battery voltage or power supply failure to the module
- Faulty master control module (gateway) managing network communication
- Incomplete or corrupted software update in the affected module
3. Symptoms You Will Notice
- Malfunction of systems controlled by the special purpose module
- Check Engine Light or other warning lights illuminated
4. Step-by-Step Diagnosis
Scan for all stored codes and note any related U-codes
Inspect CAN bus wiring and connectors for damage, corrosion, or looseness
Check battery voltage and power supply to the special purpose module
Test CAN bus termination resistors with a multimeter
Verify module communication using a scan tool; attempt to communicate with the module
If possible, swap or reprogram the module as per manufacturer procedures
5. Frequently Asked Questions
Is it safe to drive?▼
It is generally safe to drive short distances, but systems controlled by the module may not function properly. Have it diagnosed soon to avoid further issues.
How much does it cost to fix?▼
Costs vary widely depending on the cause: wiring repairs $100-$300, module replacement $400-$1200, reprogramming $100-$200.